Foldable display design

ABSTRACT

A display device includes a substrate and a display structure. The substrate has a foldable first region and a second region adjacent to the foldable first region, wherein a folding axis overlaps the foldable first region. The display structure overlaps the substrate and includes a plurality of first pixel electrodes. A minimum distance between the substrate and a top surface of one of the plurality of first pixel electrodes overlapping the foldable first region is defined as a first distance, a minimum distance between the substrate and a top surface of one of the plurality of first pixel electrodes overlapping the second region is defined as a second distance, and the first distance is less than the second distance.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation application of and claimspriority of U.S. patent application Ser. No. 15/803,830, filed on Nov.5, 2017, which claims the benefit of U.S. provisional application No.62/527,198, filed Jun. 30, 2017 and entitled “Display Apparatus”, andthe entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

Embodiments disclosed herein relate to a foldable display device andassociated method of production, and more specifically, to a foldabledisplay device having a reduced probability of damage during folding.

2. Description of the Prior Art

Foldable display devices offer portability when in a folded state, whichexpands into a relatively large sized display when in an unfolded state.Foldable display devices may have various applications in electronicdisplays used in televisions, monitors, and mobile computing devices.Some non-limiting examples of mobile computing devices includesmartphones, tablet computers, mobile personal computers (PCs), andelectronic book readers. Foldable (or flexible) display devices may havefurther applicability to wearable devices, such as smartwatches.

SUMMARY OF THE INVENTION

According to various embodiments disclosed herein, exemplary displaydevice implementations are described having a reduced probability ofdamage during folding of the display device. Such display deviceimplementations are suitable for increasing the portability and/ordurability of the display device.

One embodiment of an exemplary display device includes a substrate and adisplay structure. The substrate has a foldable first region and asecond region adjacent to the foldable first region, wherein a foldingaxis overlaps the foldable first region. The display structure overlapsthe substrate and includes a plurality of first pixel electrodes. Aminimum distance between the substrate and a top surface of one of theplurality of first pixel electrodes overlapping the foldable firstregion is defined as a first distance, a minimum distance between thesubstrate and a top surface of one of the plurality of first pixelelectrodes overlapping the second region is defined as a seconddistance, and the first distance is less than the second distance.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, may admit to other equally effective embodiments.

FIG. 1 illustrates exemplary folding axes for a display device,according to embodiments described herein.

FIG. 2 is a schematic diagram of an exemplary display device havingdifferent regions, according to embodiments described herein.

FIGS. 3A-3D illustrate exemplary folding of the display device,according to embodiments described herein.

FIG. 4 is a circuit diagram illustrating an exemplary arrangement ofdisplay driver circuitry, according to embodiments described herein.

FIG. 5 is a schematic diagram of an exemplary display device havingdifferently-sized channel regions, according to embodiments describedherein.

FIGS. 6A and 6B illustrate different configurations of a channel regionrelative to a folding axis, according to embodiments described herein.

FIGS. 7A and 7B illustrate exemplary off-axis channel regions, accordingto embodiments described herein.

FIGS. 8A, 8B, and 9 are diagrams illustrating exemplary arrangements ofchannel regions and/or display units, according to embodiments describedherein.

FIG. 10 illustrates a substrate having differently-sized thicknesses,according to embodiments described herein.

FIG. 11 is a schematic diagram illustrating differently-sized channelregions in conjunction with differently-sized substrate thicknesses,according to embodiments described herein.

FIG. 12 is a schematic diagram illustrating differently-sized displayunits in conjunction with differently-sized substrate thicknesses,according to embodiments described herein.

FIGS. 13 and 14 illustrate a display structure having differently-sizedthicknesses, according to embodiments described herein.

FIG. 15 illustrates an exemplary method of producing a foldable displaydevice, according to embodiments described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation. The drawings referred to here should not beunderstood as being drawn to scale unless specifically noted. Also, thedrawings are often simplified and details or components omitted forclarity of presentation and explanation. The drawings and discussionserve to explain principles discussed below, where like designationsdenote like elements.

DETAILED DESCRIPTION

FIG. 1 illustrates exemplary folding axes for a display device 100,according to embodiments described herein. The display device 100comprises an integrated circuit (IC) 110 disposed on a substrate 105. Inthis embodiment, the IC 110 is disposed on a relatively short side ofthe substrate 105. In other embodiment, the IC 110 may be disposed on arelatively long side of the substrate 105 or with any suitable alternatepositioning, but is not limited thereto. The IC 110 is configured tocontrol operation of display units included in the display device 100.In some embodiments, the substrate 105 includes a flexible printedcircuit board (not shown), and the IC 110 may be configured tocommunicate with an external processor through the flexible printedcircuit board.

The display device 100 comprises an active region 115 in which imageryis displayed using one or more of the display units. In someembodiments, each display unit corresponds to a respective pixel, andthe active region 115 comprises a plurality of (M×N) pixels that arearranged in a pattern of M rows and N columns, where M and N are eachpositive integers. The active region 115 may include any alternatenumber of pixels with any suitable spatial arrangement.

In some embodiments, each pixel comprises one or more sub-pixelsaccording to a predefined color model. Some examples of color modelsinclude a RGB (red, green, and blue) color model, a RGBW (red, green,blue, and white) color model, a RGBY (red, green, blue, and yellow)color model, a RGBG color model, and a RBGB color model. Other colormodels are also possible. In some embodiments, each pixel may correspondto one sub-pixel. In other embodiments, each pixel may correspond to aplurality of sub-pixels.

Each display unit (or pixel) includes one or more light-emittingelements according to any suitable display technologies, whether nowknown or later developed. Some non-limiting examples of displaytechnologies include light-emitting diodes (LEDs), organic LEDs (OLEDs),quantum dot LEDs (QLEDs), and so forth. In one embodiment, the displayunits comprise micro-LEDs having a size (e.g., a diameter or a largestdimension) between about ten micrometers (10 μm) and about one hundred(100) micrometers (100 μm). Alternately, the micro-LEDs may have a sizesuch as less than ten micrometers (10 μm) and greater than onemicrometer (1 μm).

The display device 100 may be flexible along one or more directions, andmay correspond to a display panel that is one or more of: curved,bendable, foldable, rollable, or stretchable. In some embodiments, thedisplay device 100 corresponds to one or more folding axes 120-1, 120(generically, a folding axis 120), about which the display device 100 isconfigured to be repeatably bent or folded without causing appreciabledamage to the display device 100. For example, the substrate 105 mayinclude one or more flexible or foldable regions corresponding to eachfolding axis 120, which permits other regions of the substrate 105 tohave their relative arrangement changed. For example, by folding (orotherwise bending) the foldable regions of the display device 100, thenon-flexible regions of the display device 100 may fold, slide, shift,etc. relative to each other. The flexible or foldable regions of thesubstrate 105 may include any suitable material or materials, whetherknown or later-developed. Some non-limiting examples of flexiblematerials include a polymer layer such as a thin plastic film formedfrom polyimide, polyethylene naphthalate (PEN), polyethyleneterephthalate (PET), or other suitable polymers or combination of suchpolymers. In some embodiments, the substrate 105 is substantiallyuniformly flexible. In other embodiments, the substrate 105 isrelatively more stiff or rigid in one or more non-foldable regions. Inone example, the substrate 105 may include a same material compositionin foldable regions and non-foldable regions, but has a greaterthickness in the non-foldable regions. In another example, the foldableregions and non-foldable regions of the substrate 105 have substantiallya same thickness with different material compositions.

As shown in FIG. 1, a first folding axis 120-1 overlaps the substrate105 at a region 125 that is disposed between the IC 110 and the activeregion 115. This may correspond to cases in which the IC 110 itself isnot flexible. As discussed herein, “overlapping” refers to spatialoverlap as viewed from a top view of the display device 100, thesubstrate 105, a display structure 205 or a component sublayer (FIG. 2),and so forth. In implementations having a flexible IC 110, at least partof the IC 110 may be disposed to overlap the folding axis 120, but isnot limited thereto. A second folding axis 120 overlaps the activeregion 115 of the substrate 105. Generally, each folding axis 120-1, 120may have any suitable location relative to the substrate 105. Forexample, the folding axis 120 may represent an approximate centerline ofthe active region 115, which is shown relative to a dimension X1 of theactive region 115 that is substantially perpendicular to the foldingaxis 120. In some cases, the dimension X1 corresponds to a width or alength of the active region 115, but is not limited thereto.Alternately, the folding axis 120 may represent an approximatecenterline of the display device 110, which is shown relative to adimension X2 of the display device 110 that is substantiallyperpendicular to the folding axis 120. Although the folding axes 120-1,120 are depicted as being substantially parallel to each other, othernon-parallel arrangements of folding axes 120 are also possible.Further, other suitable numbers of folding axes 120 may be implementedin the display device 100, such as one folding axis 120, or three ormore folding axes 120.

FIG. 2 is a schematic diagram 200 of an exemplary display device havingdifferent regions, according to embodiments described herein. Theschematic diagram 200 depicts a display structure 205 that overlaps thesubstrate 105 from a top view. The display structure 205 is disposed onthe substrate 105. As will be discussed below with respect to FIG. 5,the display structure 205 may comprise a display unit layer 505 and acircuit layer 510. The display unit layer 505 may comprise a pluralityof sublayers, such as an encapsulation sublayer 515, a barrier sublayer520 and a light emitting sublayer 525. The circuit layer 510 maycomprise a semiconductor sublayer 530 and a buffer sublayer 540. Layersother than the display structure 205 may also be included.

As shown in FIG. 1 and FIG. 2, the substrate 105 has a foldable firstregion 210 corresponding to the folding axis 120, and second regions215-1 and 215-2 adjacent to the foldable first region 210. The foldablefirst region 210 of the substrate 105 is disposed between the secondregions 215-1 and 215-2 (generically, a second region 215). In someembodiments, the second regions 215-1 and/or 215-2 are relatively stiffrelative to the foldable first region 210. In some cases, the relativelystiff second regions 215-1 and/or 215-2 may help to limit the bending ofthe substrate 105 to only those intended modes (e.g., around the foldingaxis 120). In other embodiments, the substrate 105 may be substantiallyuniformly flexible, such that the second regions 215-1, 215-2 are alsoflexible or foldable. As shown, the folding axis 120 overlaps with thefoldable first region 210 from a top view, and as depicted extends intoand out of the page. While a single foldable first region 210 and twosecond regions 215-1, 215-2 are depicted, alternate numbers of therespective regions are also possible.

FIGS. 3A-3D illustrate exemplary folding of the display device,according to embodiments described herein. In diagram 300, the displaystructure 205 is oriented inward when the display device is bent orfolded about the folding axis 120. In diagram 305, the display structure205 is oriented inward to a fully-folded position in which the secondregion 215-1 has a 180° orientation relative to the second region 215-2.In diagram 310, the display structure 205 is oriented outward when thedisplay device is bent or folded about the folding axis 120.

In diagram 315, the display device comprises foldable first regions210-1, 210-2, and second regions 215-1, 215-2, 215-3. A folding axis120-1 overlaps with the foldable first region 210-1, and a folding axis120-2 overlaps with the foldable first region 210-2. As shown, a firstportion of the display structure 205 that is folded around the foldingaxis 120-1 is oriented outward, and a second portion of the displaystructure 205 that is folded around the folding axis 120-2 is orientedinward.

FIG. 4 is a circuit diagram 400 illustrating an exemplary arrangement ofdisplay driver circuitry, according to embodiments described herein. Thecircuit diagram 400 may be used in conjunction with other embodimentsdescribed herein, such as for driving the display units of the displaydevice 100 of FIG. 1.

The circuit diagram 400 comprises a switch transistor 405, a drivingtransistor 410, and a reset transistor 415. The switch transistor 405 isconfigured to receive a first control signal (“Scan”) that is sharedwith the reset transistor 415. Based on the first control signal, theswitch transistor 405 is configured to conduct a data signal (“Data”)across a channel of the switch transistor 405.

The driving transistor 410 is configured to receive the data signal fromthe switch transistor 405. Based on the data signal, the drivingtransistor 410 is configured to conduct current across a channel of thedriving transistor 410 into an input node for a light-emitting element425. As shown, the driving transistor 410 is configured to couple afirst supply voltage (Vdd) with the input node. Some non-limitingexamples of the light-emitting element 425 comprise LEDs, micro-LEDs,OLEDs, and QLEDs.

A storage capacitor 420 is coupled between a control terminal of thedriving transistor 410 and the input node. The storage capacitor 420 isconfigured to maintain values of the data signal at the controlterminal.

The reset transistor 415 is configured to receive the first controlsignal. Based on the first control signal, the reset transistor 415 isconfigured to conduct a reference voltage signal (Vref) across a channelof the reset transistor 415 into the input node.

The light-emitting element 425 is coupled between the input node and asecond supply voltage (Vss; alternately “VCOM” or “ground”). As shown,an anode of the light-emitting element 425 is connected with the inputnode, and a cathode of the light-emitting element 425 is connected withVss. However, other implementations may have the anode and cathode ofthe light-emitting element 425 reversed.

FIG. 5 is a schematic diagram 500 of an exemplary display device havingdifferently-sized channel regions, according to embodiments describedherein. The display device may be used in conjunction with otherembodiments described herein, such as the display device depicted inFIG. 2 and/or the circuit diagram 400 of FIG. 4.

The schematic diagram 500 includes the display structure 205 overlappingthe substrate 105. Although shown as a single element, the substrate 105may include a plurality of elements, such as a flexible substrate layer,a supporting film layer, a supporting film adhesive, and so forth.

The display structure 205 comprises a display unit layer 505 overlappinga circuit layer 510. The display unit layer 505 comprises anencapsulation sublayer 515 that defines an external surface of thedisplay device 100. The encapsulation sublayer 515 overlaps a lightemitting sublayer 525, which are interspersed with sections of a barriersublayer 520. Described differently, the barrier sublayer 520 forms aplurality of openings and the light emitting sublayer 525 is formed inthe plurality of openings. Although not specifically labeled, thedisplay unit layer 505 may comprise conductive connections above (i.e.,between the encapsulation sublayer 515 and the light emitting sublayer525, and may be defined as a cathode) and below (i.e., between the lightemitting sublayer 525 and the circuit layer 510, and may be defined asan anode) the light emitting sublayer 525. In other words, overlapping(from top view) of the conductive connection above (i.e., the cathode),the light emitting sublayer 525 and the conductive connections below(i.e., the anode) may be defined as a plurality of light-emittingelements 425.

The schematic diagram 500 comprises a plurality of display units 545,each of which comprises a respective transistor implemented in thecircuit layer 510, and the respective light-emitting element 425.Although not specifically labeled, the circuit layer 510 may include oneor more electrically insulative sublayers for insulating variouscomponents of the circuit layers 510. For example, the circuit layer 510comprises a buffer sublayer 540 arranged between the transistors and thesubstrate 105.

In some embodiments, a first transistor 550-1 overlaps the foldablefirst region 210 and has a first channel region 535-1 with a firstdimension B1 along a first direction D1 that is substantiallyperpendicular to the folding axis 120. A second transistor 550-2overlaps the second region 215 and has a second channel region 535-2with a second dimension B2 along the first direction D1. The firstdimension B1 is less than the second dimension B2. In some embodiments,the first transistor 550-1 and the second transistor 550-2 are each arespective driving transistor 410, but are not limited thereto. In otherembodiments, the first transistor 550-1 and/or the second transistor550-2 are other transistors included in the display structure 205. Insome embodiments, the display structure 205 further comprises a firstpixel electrode 555-1 connected with the first transistor 550-1, and asecond pixel electrode 555-2 connected with the second transistor 550-2.

Each transistor comprises a gate terminal (“Gate”), a source terminal(“Source”) and a drain terminal (“Drain”), wherein the source terminal(“Source”) and the drain terminal (“Drain”) are coupled with asemiconductor sublayer 530 of the circuit layer 510. As shown, a firstchannel region 535-1 of the first transistor 550-1 within the foldablefirst region 210 corresponds to a first dimension (or breadth) B1 alonga first direction D1. The first direction D1 is substantiallyperpendicular to the folding axis 120, and is also substantiallyparallel to the substrate 105. A second channel region 535-2 of thesecond transistor 550-2 disposed within the second region 215corresponds to a second dimension B2 along the first direction D1.

The channel regions 535-1 disposed in the foldable first region 210 maybe particularly susceptible to damage in response to folding or bendingthe display device. Sustained damage to the channel regions 535-1changes the properties of the corresponding first transistor 550-1,which can affect the quality of light emitted by the light-emittingelement 425.

In some embodiments, a first channel region 535-1 of the firsttransistor 550-1 within the foldable first region 210 is differentlysized than a second channel region 535-2 of the second transistor 550-2disposed within the second region 215. In some embodiments, the firstdimension B1 and the second dimension B2 are controlled according toEquation (1):0.3≤(B1/B2)≤0.95  (1)

In other words, a ratio of the first dimension B1 to the seconddimension B2 is greater than or equal to 0.3 and less than or equal to0.95. In some embodiments, sizing the first channel region 535-1 to havea smaller first dimension B1 than the second dimension B2 operates toreduce the probability of sustaining damage within the first channelregion 535-1, which results in an increased reliability of the displaydevice.

FIGS. 6A and 6B illustrate different configurations 600, 605 of achannel region 535-1 relative to a folding axis 120, according toembodiments described herein. The configurations 600, 605 may be used inconjunction with other embodiments described herein, such as the displaydevice depicted in FIG. 5. In the configuration 600, the first dimensionB1 along the first direction D1 (substantially perpendicular to thefolding axis 120) corresponds to a length L1 of the channel region 535-1of a thin film transistor. In the configuration 605, the first dimensionB1 corresponds to a width W1 of the channel region 535-1 of a thin filmtransistor.

FIGS. 7A and 7B illustrate exemplary off-axis channel regions 535,according to embodiments described herein. Configurations 700, 710 maybe used in conjunction with other embodiments described herein, such asthe display device depicted in FIG. 5. Configuration 700 illustrates acontinuous channel region 535 having a long axis that is “off-axis”—inother words, the long axis has an orientation that is neither parallelto the folding axis 120, nor parallel to the first direction D1. In sucha case, the extent of the channel region 535 in the first direction D1is graphically illustrated using a bounding box 705. The bounding box705 is a minimum rectangle to define the channel region 535 with sidesparallel to or perpendicular to the folding axis 120. The firstdimension B1 of the channel region 535 may be determined as thedimension of the bounding box 705 in the first direction D1. Thedetermined first dimension B1 may be used in conjunction with Equation 1to determine the relative sizing of the channel regions 535 of differentregions of the display device.

Configuration 710 illustrates a distributed (or discontinuous) channelregion comprising a first channel region 535-1 and a second channelregion 535-2 for a transistor. As shown, a dimension B1-1 of the firstchannel region 535-1 (defined by a side of a bounding box 705-1perpendicular to the folding axis 120) is less than a dimension B1-2 ofthe second channel region 535-2 (defined by a side of a bounding box705-2 perpendicular to the folding axis 120). The larger of thedimension B1-1, B1-2 may be used in conjunction with Equation 1 (in thisembodiment, the dimension B1-2 is used to represent the dimension of thechannel region) to determine the relative sizing of the channel regions535 of different regions of the display device.

Further, while FIGS. 6A, 6B, 7A, and 7B illustrate exemplary channelregions corresponding to individual transistors, the person of ordinaryskill will understand that the channel regions for the varioustransistors of a display device need not be identical, but may havedifferent dimensions and/or orientations and/or shapes. For example, thetransistors within a particular region (e.g., the foldable first region210, the second region 215-1, or the second region 215-2) may besubstantially identical, or may differ from each other. Further, thetransistors within one region may be different from transistors withinanother region.

FIGS. 8A, 8B, and 9 are diagrams illustrating exemplary arrangements800A, 800B, 900 of channel regions 535 and/or display units 425,according to embodiments described herein. More specifically, thefeatures discussed with respect to the arrangements 800A, 800B, 900 maybe applicable to display device implementations.

As discussed above with respect to FIG. 5, and as illustrated inarrangement 800A, a first area A1 of one of the display units 425 in thefoldable first region 210 is less than a second area A2 of one of thedisplay units 425 in the second region 215-1 and/or the second region215-2. The first area A1 and/or the second area A2 may be defined as anarea of one of the openings of the barrier layer 520 from a top view. Insome embodiments, having a smaller first area A1 operates to reduce theprobability of sustaining damage within the foldable first region 210,which results in an increased reliability of the display device. Thus,in one embodiment, a plurality of first display units 425 are arrangedto overlap the foldable first region 210 and a plurality of seconddisplay units 425 are arranged to overlap the second region 215-1 and/orthe second region 215-2, and wherein a first area A1 of one firstdisplay unit 425 of the plurality of first display units is less than asecond area A2 of one second display unit 425 of the plurality of seconddisplay units.

In some embodiments, and as illustrated in arrangement 800B, a firstdimension B1 of one of a channel region 535 in the foldable first region210 may be smaller than a second dimension B2 of one of a channel region535 in the second region 215-1 and/or the second region 215-2 in thefirst direction D1. In some embodiments, the relative proportions of thefirst dimension B1 and second dimension B2 may be controlled accordingto Equation (1).

In some embodiments, and as illustrated in arrangement 900, a firstspacing distance S1 may be defined between adjacent first channelregions 535 of the first transistors of the foldable first region 210,and a second spacing distance S2 may be defined between adjacent secondchannel regions 535 of the second transistors of the second regions215-1, 215-2. The first spacing distance S1 and the second spacingdistance S2 are defined as a minimum distance between adjacent channelregions relative to the first direction D1. The first spacing distanceS1 may be greater than the second spacing distance S2.

Thus, in one embodiment, a plurality of first transistors are arrangedto overlap the foldable first region 210 and a plurality of secondtransistors are arranged to overlap the second region 215-1, 215-2,wherein first channel regions 535 of two adjacent first transistors areseparated by a first spacing distance S1 along the first direction D1,wherein second channel regions 535 of two adjacent second transistorsare separated by a second spacing distance S2 along the first directionD1, and wherein the first spacing distance S1 is greater than the secondspacing distance S2.

Alternatively, the first spacing distance S1 may be defined betweenadjacent display units 425 of the foldable first region 210, and thesecond spacing distance S2 may be defined between adjacent display units425 of the second regions 215-1, 215-2. The first spacing distance S1and the second spacing distance S2 are defined as a minimum distancebetween adjacent display units relative to the first direction D1.Again, the first spacing distance S1 may be greater than the secondspacing distance S2. In some embodiments, additional spacing betweenadjacent channel regions 535 and/or display units 425 operates to reducethe probability of sustaining damage within the foldable first region210, which results in an increased reliability of the display device.Thus, in one embodiment, two adjacent first display units 425 areseparated by a first spacing distance S1 along the first direction D1,wherein two adjacent second display units 425 are separated by a secondspacing distance S2 along the first direction D1, and wherein the firstspacing distance S1 is greater than the second spacing distance S2.

Further, while FIGS. 8A, 8B, and 9 illustrate exemplary spacingdistances S1, S2 corresponding to individual channel regions 535 and/orindividual display units 425, the person of ordinary skill willunderstand that the spacing distances S1, S2 between channel regions 535and/or display units 425 of the display device need not be identical,but may have different spacing distances. For example, the spacingdistances within a particular region (e.g., the foldable first region210, the second region 215-1, or the second region 215-2) may besubstantially identical, or may differ from each other. Further, thespacing distances within a particular region may be different fromspacing distances within another region.

In some embodiments, the different spacing distances S1, S2 may be usedin conjunction with the different dimensions B1, B2 of the channelregions 535 and/or the different areas A1, A2 of the display units.

In some embodiments, the plurality of first display units 425 arearranged to overlap (from a top view) the foldable first region 210 witha first repeating pattern. The plurality of second display units 425 arearranged to overlap (from a top view) the second regions 215-1, 215-2with a second repeating pattern. The first repeating pattern might bedifferent from the second repeating pattern, but is not limited thereto.For example, the first repeating pattern and/or the second repeatingpattern may be rectangular grids with different-sized display units 425and/or different spacing distance between adjacent first display units425 or adjacent second display units 425. In other embodiments, thefirst repeating pattern and/or the second repeating pattern may bePenTile, but is not limited thereto.

In some embodiments, a first channel region 535 of the foldable firstregion 210 comprises a first semiconductor material, and a secondchannel region 535 of the second regions 215-1, 215-2 comprises a secondsemiconductor material. The first semiconductor material and the secondsemiconductor material may be the same or may be different. For example,the first semiconductor material and the second semiconductor materialmay comprise low-temperature polysilicon (LTPS), indium gallium zincoxide (IGZO), polysilicon, amorphous silicon, or so forth.

In one embodiment, the first channel region 535 comprises a firstsemiconductor material and the second channel region 535 comprises adifferent second semiconductor material. In one non-limiting example,the first semiconductor material used in the foldable first region 210comprises LTPS, and the second semiconductor material used in the secondregions 215-1, 215-2 comprises IGZO. In some cases, the firstsemiconductor material may be selected to provide a greater flexibilityto the foldable first region 210 and/or to provide a greater reliabilityfor the transistors arranged in the foldable first region 210. Thedifferent semiconductor materials may be used in conjunction with any ofthe other features discussed herein.

FIG. 10 illustrates a substrate having differently-sized thicknesses,according to embodiments described herein. In diagram 1000, thesubstrate 105 has a first thickness T1 in the foldable first region 210,and a second thickness T2 in the second regions 215-1, 215-2. The firstthickness T1 corresponds to a relatively flat area in the foldable firstregion 210, and the second thickness T2 corresponds to a relatively flatarea in the second regions 215-1, 215-2. The first thickness T1 is lessthan the second thickness T2. The first thickness T1 and the secondthickness T2 are measured along a direction perpendicular to the firstdirection D1. Thus, in one embodiment, the substrate 105 has a firstthickness T1 in the foldable first region 210 and has a second thicknessT2 in the second region 215-1, 215-2, and wherein the first thickness T1is less than the second thickness T2.

Based on the manufacturing process, the transition between the firstthickness T1 and the second thickness T2 may be substantially immediateor may be gradual. For example, an anisotropic etching of the substrate105 may provide substantially vertical walls extending from the secondthickness T2 to the first thickness T1.

In some embodiments, the reduced first thickness T1 in the foldablefirst region 210 makes the display device easier to fold and reduces theprobability of sustaining damage within the foldable first region 210.The different substrate thicknesses T1, T2 may be used in conjunctionwith any of the other features discussed herein.

FIG. 11 is a schematic diagram 1100 illustrating differently-sizedchannel regions in conjunction with differently-sized substratethicknesses, according to embodiments described herein. As shown, one ofthe channel regions 535 within the foldable first region 210 has a firstdimension B1 in the first direction D1, and one of the channel regions535 within the second regions 215-1, 215-2 has a second dimension B2 inthe first direction D1. Additionally, the first thickness T1 in thefoldable first region 210 is less than the second thickness T2 in thesecond regions 215-1, 215-2.

In some embodiments, the dimensions B1, B2 are controlled according toEquations (2, 3):(0<(T1/T2)≤0.5)→0.2≤(B1/B2)≤0.8  (2)(0.5<(T1/T2)<1)→0.4≤(B1/B2)≤0.95  (3)

In other words, when a first ratio of the first thickness T1 to thesecond thickness T2 is greater than zero and less than or equal to 0.5,a second ratio of the first dimension B1 to the second dimension B2 isgreater than or equal to 0.2 and less than or equal to 0.8. When thefirst ratio is greater than 0.5 and less than 1, the second ratio isgreater than or equal to 0.4 and less than or equal to 0.95. In someembodiments, sizing the thicknesses T1, T2 and the dimensions B1, B2according to Equations (2, 3) operates to reduce the probability ofsustaining damage within the first channel region 535, which results inan increased reliability of the display device.

FIG. 12 is a schematic diagram 1200 illustrating differently-sizeddisplay units 545 in conjunction with differently-sized substratethicknesses, according to embodiments described herein. As shown, one ofthe display units 545 within the foldable first region 210 has a widthW1 in the first direction D1, and one of the display units 545 withinthe second regions 215-1, 215-2 has a width W2 in the first directionD1. The width W1 is a maximum width of one of the display unit 545within the foldable first region 210 in the first direction D1, and thewidth W2 is a maximum width of one of the display unit 545 within thesecond regions 215-1, 215-2 in the first direction D1. Additionally, thefirst thickness T1 in the foldable first region 210 is less than thesecond thickness T2 in the second regions 215-1, 215-2.

In some embodiments, the widths W1, W2 are controlled according toEquations (4, 5):(0<(T1/T2)≤0.5)→0.3≤(W1/W2)≤0.8  (4)(0.5<(T1/T2)<1)→0.5≤(W1/W2)≤0.95  (5)

In other words, when a first ratio of the first thickness T1 to thesecond thickness T2 is greater than zero and less than or equal to 0.5,a second ratio of the width W1 to the width W2 is greater than or equalto 0.3 and less than or equal to 0.8. When the first ratio is greaterthan 0.5 and less than 1, the second ratio is greater than or equal to0.5 and less than or equal to 0.95. In some embodiments, sizing thethicknesses T1, T2 and the widths W1, W2 according to Equations (4, 5)operates to reduce the probability of sustaining damage within the firstchannel region 535, which results in an increased reliability of thedisplay device.

FIGS. 13 and 14 illustrate a display structure 205 havingdifferently-sized thicknesses, according to embodiments describedherein. In diagram 1300, the substrate 105 has a substantially constantthickness, and the display structure 205 overlapping the substrate 105.In one embodiment, the display structure 205 has a third thickness T3 inthe foldable first region 210, and a fourth thickness T4 in the secondregions 215-1, 215-2. The third thickness T3 corresponds to a relativelyflat area in the foldable first region 210, and the fourth thickness T4corresponds to a relatively flat area in the second regions 215-1,215-2. The third thickness T3 is less than the fourth thickness T4.Based on the manufacturing process, the transition between the thirdthickness T3 and the fourth thickness T4 may be substantially immediateor may be gradual. For example, an anisotropic etching of the displaystructure 205 (or one or more component sublayers) may providesubstantially vertical walls extending from the fourth thickness T4 tothe third thickness T3.

In some embodiments, the reduced third thickness T3 in the foldablefirst region 210 makes the display device easier to fold and reduces theprobability of sustaining damage within the foldable first region 210.The different display structure 205 thicknesses T3, T4 may be used inconjunction with any of the other features discussed herein. Forexample, the reduced third thickness T3 may be used in conjunction withany of: reduced thickness of the substrate 105, reduced dimensions ofthe channel regions 535, and reduced size of the display units 545.

Thus, in one embodiment, the display structure 205 overlaps thesubstrate 105, wherein the display structure 205 has a first thicknessT3 overlapping the foldable first region 210 and has a second thicknessT4 overlapping the second region 215-1, wherein the first thickness T3is less than the second thickness T4.

In diagram 1400, the reduced third thickness T3 in the foldable firstregion 210 is achieved using one or more sublayers of the displaystructure 205. For example, the encapsulation sublayer 515, the barriersublayer 520, and/or an insulating sublayer 1405 disposed beneath thebarrier sublayer 520 may have a reduced thickness in the foldable firstregion 210.

Thus, in one embodiment, the encapsulation sublayer 515 has a thirdthickness overlapping the foldable first region 210 and has a fourththickness overlapping the second region 215-1, 215-2, wherein the thirdthickness is less than the fourth thickness. In another embodiment, theinsulating sublayer 1405 has a third thickness overlapping the foldablefirst region 210 and having a fourth thickness overlapping the secondregion 215-1, 215-2, wherein the third thickness is less than the fourththickness.

FIG. 15 illustrates an exemplary method 1500 of producing a foldabledisplay device, according to embodiments described herein. The method1500 may be used in conjunction with other embodiments described herein,such as the display devices depicted in FIGS. 5 and 11. The method 1500may be performed using manufacturing processes known to one of ordinaryskill in the art.

The method 1500 begins at block 1505, where a plurality of firsttransistors are arranged to overlap a foldable first region of asubstrate, wherein a folding axis overlaps the foldable first region.Each of the plurality of first transistors has a respective firstchannel region with a first dimension along a first directionsubstantially perpendicular to the folding axis. The first direction mayalso be substantially parallel to the substrate.

At block 1515, a plurality of second transistors are arranged to overlapa second region of the substrate adjacent to the foldable first region.Each of the plurality of second transistors has a respective secondchannel region with a second dimension along the first direction. Thefirst dimension is less than the second dimension. In some embodiments,blocks 1505 and 1515 are performed at different times (e.g.,manufactured separately). In other embodiments, blocks 1505 and 1515 areat least partly overlapping in time. In yet other embodiments, blocks1505 and 1515 are entirely overlapping in time.

In some embodiments, at block 1525, a plurality of first display unitsare arranged to overlap the foldable first region. At block 1535, aplurality of second display units are arranged to overlap the secondregion. A first area of one of the plurality of first display units isless than a second area of one of the plurality of second display units.

In some embodiments, the plurality of first display units are arrangedto overlap the foldable first region with a first repeating pattern, andthe plurality of second display units are arranged to overlap the secondregion with a second repeating pattern.

In some embodiments, blocks 1525 and 1535 are performed at differenttimes (e.g., manufactured separately). In other embodiments, blocks 1525and 1535 are at least partly overlapping in time. In yet otherembodiments, blocks 1525 and 1535 are entirely overlapping in time.Method 1500 ends following completion of block 1535.

The various illustrative logical blocks, modules, circuits, andalgorithm steps described in connection with the aspects disclosedherein may be implemented as electronic hardware, computer software, orcombinations of both. Various changes and modifications may be madeherein without departing from the scope of the appended claims. Further,the functions, steps, or actions described in the method claims inaccordance with aspects described herein need not be performed in anyparticular order unless expressly stated otherwise.

In view of the foregoing, the scope of the present disclosure isdetermined by the claims that follow.

What is claimed is:
 1. A display device, comprising: a substrate havinga foldable first region and a second region adjacent to the foldablefirst region, wherein a folding axis overlaps the foldable first region;and a display structure overlapping the substrate and comprising aplurality of first pixel electrodes; wherein a minimum distance betweenthe substrate and a topmost surface of one of the plurality of firstpixel electrodes overlapping the foldable first region is defined as afirst distance, a minimum distance between the substrate and a topmostsurface of one of the plurality of first pixel electrodes overlappingthe second region is defined as a second distance; wherein the firstdistance is less than the second distance.
 2. The display device ofclaim 1, further comprising an insulating layer disposed between theplurality of first pixel electrodes and the substrate, the insulatinglayer comprising: a first portion overlapping the foldable first region;and a second portion overlapping the second region; wherein a thicknessof the first portion is less than a thickness of the second portion. 3.The display device of claim 1, the display structure further comprisingan encapsulation layer disposed on the plurality of first pixelelectrodes and comprising: a first portion overlapping the foldablefirst region; and a second portion overlapping the second region;wherein a thickness of the first portion is less than a thickness of thesecond portion.
 4. The display device of claim 1, wherein a width of oneof the plurality of first pixel electrodes overlapping the foldablefirst region in a first direction is less than a width of one of theplurality of first pixel electrodes overlapping the second region in thefirst direction.
 5. The display device of claim 4, wherein the firstdirection is substantially perpendicular to the folding axis.
 6. Thedisplay device of claim 1, wherein a first area of one of the pluralityof first pixel electrodes overlapping the foldable first region is lessthan a second area of one of the plurality of first pixel electrodesoverlapping the second region.
 7. The display device of claim 1, whereintwo adjacent ones of the plurality of first pixel electrodes overlappingthe foldable first region are separated by a first spacing distancealong a first direction, two adjacent ones of the plurality of firstpixel electrodes overlapping the second region are separated by a secondspacing distance along the first direction, and the first spacingdistance is greater than the second spacing distance.
 8. The displaydevice of claim 7, wherein the first direction is substantiallyperpendicular to the folding axis.
 9. The display device of claim 1,wherein the substrate has a first thickness in the foldable first regionand has a second thickness in the second region, and the first thicknessis less than the second thickness.
 10. The display device of claim 9,wherein a first ratio of the first thickness to the second thickness isgreater than zero and less than or equal to 0.5, wherein the displaystructure further comprises a plurality of display units, each of theplurality of display units comprises one of the plurality of first pixelelectrodes, and a second ratio of a width of one of the plurality ofdisplay units overlapping the foldable first region in a first directionto a width of one of the plurality of display units overlapping thesecond region in the first direction is greater than or equal to 0.3 andless than or equal to 0.8, and wherein the first direction issubstantially perpendicular to the folding axis.
 11. The display deviceof claim 9, wherein a first ratio of the first thickness to the secondthickness is greater than 0.5 and less than 1, wherein the displaystructure further comprises a plurality of display units, each of theplurality of display units comprises one of the plurality of first pixelelectrodes, and a second ratio of a width of one of the plurality ofdisplay units overlapping the foldable first region in a first directionto a width of one of the plurality of display units overlapping thesecond region in the first direction is greater than or equal to 0.5 andless than or equal to 0.95, and wherein the first direction issubstantially perpendicular to the folding axis.
 12. The display deviceof claim 9, wherein a transition between the first thickness and thesecond thickness is immediate or gradual.
 13. The display device ofclaim 1, wherein the display structure further comprises a plurality ofsecond pixel electrodes disposed on the plurality of the first pixelelectrodes.
 14. The display device of claim 1, wherein a thickness ofthe display structure in the foldable first region is less than athickness of the display structure in the second region.
 15. The displaydevice of claim 1, wherein the plurality of first pixel electrodes arerespectively comprised in different light emitting diodes (LEDs),different organic light emitting diodes (OLEDs), different quantum dotLEDs (QLEDs), or different micro-LEDs.
 16. The display device of claim1, wherein the substrate further has another second region adjacent tothe foldable first region, and the foldable first region is disposedbetween the second regions.
 17. The display device of claim 16, whereinone of the second regions has a 180° orientation relative to another oneof the second regions when folding the display device.
 18. The displaydevice of claim 1, wherein the display structure further comprises: afirst transistor overlapping the foldable first region, and the firsttransistor being connected with one of the plurality of first pixelelectrodes overlapping the foldable first region; and a secondtransistor overlapping the second region, and the second transistorbeing connected with one of the plurality of first pixel electrodesoverlapping the second region.
 19. The display device of claim 18,wherein the first transistor comprises a first semiconductor material,and the second transistor comprises a second semiconductor materialdifferent from the first semiconductor material.
 20. The display deviceof claim 18, wherein each of the first transistor and the secondtransistor is connected with a capacitor.